The present invention relates generally to transmission shafts for transmitting drive power in various types of machinery, and more particularly to a transmission shaft which is capable of having its overall length varied.
Transmission shafts which are associated with a pair of sliding parallel or synchronous speed torque coupling joints are known in the art such as from German PS No. 1,914,275. The transmission shaft known from this prior art, however, might have to be cut and shortened to a different length if it is desired to use this shaft in different applications. For example, if such a shaft is to be applied to weaving looms or other textile machinery, dimensional requirements of the machinery might necessitate altering the length of the shaft at the time of installation. This therefore requires that the shaft have a particular longitudinal dimension to permit removal and reassembly in a new machine. Different coupling joints might have to be used, or it might have to be provided with a pin to be welded into the shaft for properly securing the shaft after it is cut and readjusted to a new length.
The prior art also includes cardanshafts which are associated with a pair of universal joints of the cruciform of cardan type and which have separate means for longitudinal adjustment using splined shaft arrangements. In such arrangements, means for accommodating length variations between the coupling joints as a result of vibrations of other kinetic effects of the machinery have been provided. Attempts to accommodate such length variations have included the provision of intermediate shafts of various lengths for use in different applications. These solutions, however, have been found to be inadequate since they also involve the possibility of cutting or trimming the length of the intermediate shafts in order for the transmission shaft to be accommodated within certain space requirements. Additionally, when using such intermediate shafts, each shaft must be provided with connector flanges which must be in precise parallel alignment or else the output of the shaft may not have the required synchronous speed. To achieve the required alignment of the various intermediate shafts is an extremely laborious and time consuming operation. Additionally, length adjustments can only be accomplished using splined shaft arrangements, however, this causes considerable thrust forces and heavy wear on the transmission shaft parts. Further, cruciform joint bearings usually require regular lubrication for satisfactory operation.
It is accordingly an object of the present invention to provide a drive transmission shaft which has a readily variable length for easy adaptation to various dimensional requirements when used in different applications, and is also capable of automatically adjusting to minor variations in the distance between the coupling joints as a result of vibrations or other forces acting on various portions of the machine.
More specifically, it is an object of the present invention to provide a variable length drive transmission shaft having a pair of torque transmitting coupling joints with a connecting shaft carried between the coupling joints having telescopically cooperating shaft members arranged for sliding movement with respect to each other to thereby enable the overall length of the transmission shaft to be varied in order to fit various dimensional requirements or to automatically adjust to minor length variations in the distance between the coupling joints.